Attempts have been made to provide an efficient and effective intake air supply system for engines. One such example, utilizes a turbocharger or twin turbochargers to increase the intake air supply to the engine increasing boost pressure and increasing output power. Thus, an exhaust gas from the engine which would be spent to the atmosphere is used by recovering the heat within the exhaust to drive a turbine, increasing efficiency. With the engine operating at or near high speed, an adequate supply of exhaust is available to drive the turbocharger and produce an efficient and effective air supply system for engines. However, at low speed sufficient exhaust to drive the turbocharger and produce an adequate supply of intake air is not available. Thus, the efficiency and effectiveness of the turbocharger is lost.
Other attempts have been made to provide and efficient and effective intake air supply for engines by incorporating a supercharger or blower. In these applications, a supercharger or blower is mechanically driven by the engine such as by a belt connected to a pulley on a crankshaft or by a gear or plurality of gears driven by the engine. With these systems, the low speed engine efficiency and effectiveness can be overcome by having a fixed speed ratio between the engine and the supercharger. For example, the speed of the supercharger can be 2 or 3 times that of the engine speed. Thus, the output of the supercharger at low engine speed can deliver adequate intake air for efficient and effective engine operation at low speed. The major disadvantage of using the supercharger is that power of the engine is used to drive the supercharger and can not be deliver as output power.
Attempts have also been made to combine the turbocharger system and the supercharger system. An example of one such system is disclosed in U.S. Pat. No. 4,903,488 issued to Noriyoshi Shibata on Feb. 27, 1990. The patent discloses a multiple compressed air supply system. A turbocharger is driven by an exhaust from an engine and a supercharger is drivingly connected to the engine by a belt and is driven by a crankshaft. The supercharger is driven at a constant speed relative to an engine speed. Thus, the effectiveness and efficiency of each system can be combined. However, with the system as disclosed, the efficiency and the effectiveness of the engine can be further improved.
The present invention is directed to overcoming one or more of the problems as set forth above.